Process of treating waste water

ABSTRACT

In a process of removing ferricyanide ions and/or ferrocyanide ions from a waste solution or water containing these ions formed in photographic processings by bringing the waste solution in contact with a weakly-basic anion-exchange resin to absorb the ferricyanide ions and/or ferrocyanide ions on the anion-exchange resin, an alkaline concentrate of the ferricyanide ions and/or ferrocyanide ions is formed by immersing the weakly-basic anionexchange resin having absorbed thereon the ions and after adding to the concentrate a strong alkali, a hypochlorite, and bromide ions to increase the pH of the concentrate to above 12, the mixture is heated to temperatures over 50*C at normal pressure, whereby the ferricyanide ion and/or ferrocyanide ions are decomposed.

United States Patent [1 1 Abe et al.

[ 1 Sept. 30, 1975 PROCESS OF TREATING WASTE WATER [75] Inventors: AkiraAbe; Yoshio Usui, both of Tokyo, Japan [22] Filed: Oct. 18, 1973 [2]]Appl. N0.: 407,760

[30] Foreign Application Priority Data Oct. 23, 1972 Japan 47-l06060[52] US. Cl 210/32; 96/60 BF; 210/37 [51] Int. Cl. B01D 15/04; BOlD15/06 [58] Field of Search 96/50 R, 60 R, 60 BF, 92; 210/24, 30, 32, 37;423/22; 75/101 BE ['56] References Cited UNITED STATES PATENTS 2,515,9307/1950 Seary 6/60 R 2,61 L699 9/1952 Zappert, 96/60 R 2,61 L700 9/l952Brunner, Jr. et al.... 96/60'R 2,944,895 7/l960 West et al. 961/60 R3,001,868 9/l96l Aveston ct a1 423/22 OTHER PUBLICATIONS ChemicalAbstracts: 72:59556a; 69:80027b;

Primary ExaminerSamih N. Zaharna Assistant Examiner-Robert H. SpitzerAttorney, Agent, or FirmSughrue, Rothwell, Mion, Zinn & Macpeak [57]ABSTRACT In a process of removing ferricyanide ions and/or fcrrocyanideions from a waste solution or water containing these ions formed inphotographic processings by bringing the waste solution in Contact witha weaklybasie anion-exchange resin to absorb the ferricyanide ionsand/or ferrocyanide ions on the anion-exchange resin, an alkalineconcentrate of the tcrricyanide ions and/or ferrocyanide ions is formedby immersing the weakly-basic anion-exchange resin having absorbedthereon the ions and after adding to the concentrate a strong alkali, ahypochlorite, and bromide ions to increase the pH of the concentrate toabove 12, the mixture is heated to temperatures over 50C at normalpressure, whereby the ferricyanide ion and/or ferrocyanide ions aredecomposed.

19 Claims, N0 Drawings PROCESS OF TREATING WASTE WATER BACKGROUND OF THEINVENTION 1. Field of the Invention The present invention relates to aprocess of treating waste water containing ferricyanide ions and/orferrocyanide ions. More particularly, the. invention relates to aprocess of treating waste water containing ferricyanide ions and/orferrocyanide ions from photographic processings. 1

The explanation of the invention given hereinafter is with respect tothe treatment of waste water in photographic processings as a specificexample but. it will be easily understood that the subject ofthisinvention is not limited to the photographic case only and the in?vention can be widely applied to general industrial waste solutionscontaining ferricyanideions and/or fer.-

rocyanide ions, such as a waste solution in galvanizing or printing anda waste solution used for the syntheses of dyes, pigments, etc., as anoxidizing agent. I

2. Description of the Prior Art The processing steps for photographicmaterials include frequently a bleach step. The bleach step is a step inwhich a metal such as silver formed by development is converted intosilver ions using an oxidizing agent and the bleach step is includedusually in the processings of silver halide color photographic materialson photographic materials for the silver dye bleach method as well as inthe reduction processings of photographic materials for making printingplates.

The reduction operation as described above is the step of oxidizing themetallic silver formed by development into silver ions and dissolvingthe silver ions. Thus, the reduction operation is conducted, when theimage density of a photographic material becomes higher than anappropriate value after developrnent caused by excessive light exposure,to reduce the image density to the appropriate range oris conducted tocontrol the properties of the dot imagesof a photographic printing plateformed by developing .a photographic material for making .a printingplate. 5

As a reducer used for the reductionv step, Farmers reducer consisting ofa solution containing a ferricya-v nide and a thiosulfate has widelybeen used. Although a permanganate oratpersulfate can also be used forthe reducer as anotheroxidizing agent than the ferricyanide, the Farmersreducer containing the ferricyanide and the thiosulfate ismost excellentdue to its-usable oxidation-reduction actions of them and hence thefa-'- tigued reducer must be dischargd.- Also, since the reducer is usedin such a manner that a printing plate is,

after being wetted well with water, immersedin the reducer, withdrawnfrom the reducer, and then washed.

with water orthat the reduceris applied onto the surface ofa printingplate while washingthe surface of the I printing plate continuously withwater, thus the reducer is contained in the washing water. Consequently,the waste water from the reduction step contains ferricyanide ionsand/or ferrocyanide ions, which are there duction products of theferricyanide ions, together with I the thiosulfate. l

The ferricyanide ions and/or the ferrocyanide ions are quite stablecomplex ions having almost no toxicity but it is known that when'thoseions are subjected to photochemical oxidation, they are decomposed toform toxic free cyanides (see, e.-g:., Yu Yiu Lurc and V. A. Panova;Behavior of Cyano Compounds in Water Ponds, Gidrokhim; Materialy,31133-143 (1964), and George Edgar and Morris Lipschuets; Toxicity ofFerroand Ferricyanide Solutions to Fish and Determination of the Causeof Mortality, Trans. Am. Fish $00., 78,192 (1948)).

According to the present discharge standards into rivers, theallowablelimit in Japan for the amount of cyanide is one ppm. The ferricyanideions and/or ferrocyanide ions have the latent toxicity as describedabove and hence the aforesaid standard is as a matter of course appliedto those ions as well. Therefore, it is necessaray to take somecounteraction in the case of discharging waste water containing thoseions.

The concentration of the ferricyanide ions and/or ferrocyanide ions inthe waste water from the reduction step using Farmers reducer is fairlylow because a large amount of water is used for washing in the reductionstep but the concentration is nevertheless higher than the dischargestandard as indicated above: Furthermore, sincelfree cyanide formed bythe photochemical decomposition of ferricyanide ions and/or ferrocyanideions is quite high in toxicity as mentioned above, the ferricyanide ionsand/or ferrocyanide ions present even in a considerably lowconcentration must be removed.

As the processes of removing those ferricyanide ions and/or ferrocyanideions from wastesolutions containing them, there are known a process ofremoving them by precipitation utilizing the reaction thereof and ironsalt, an electrodialysis process, a reverse osmosis process, acombustion process, a pyrolysis process, and an ion exchange process.

The process of removing ferricyanide ions and/or ferrocyanide ions byprecipitation as the result of the reaction with an iron salt utilizesthe phenomenon of the formation by these ions of Prussian Blue by thereaction with iron salt ions (see, Japanese Pat. application However,this process has the disadvantage that a long time is required toprecipitate the particles of Prussian Blue since the particles are veryfine and, in particular, when the waste solution to 'be treated is lowin concentration and contains a large amount of water such as the wastewater from the reduction step or waste water of the reducer, the processrequires equipment with a large capacity. This process has further thedisadvantage that since the precipitates formed contain ferricyanideand/or ferrocyanide, they may not be discharged as they are and hencemust be treated further.

Electrodialysis and reverse osmosis may be effective processes fortreating waste water containing ferricyaamount of water such as thewaste water from the reduction step,-'-a" verylargeequipment isrequiredand hence the cost for the equipment is quite high.

The combustion process is a process of evaporating water and decomposingthe residue unde'r'heating to a high temperature by means of a heavyoil. burner, etc.

However, in order to apply this process to the waste reducer solutioncontaining ferricyanide ions and/or ferrocyanide ions, a quite largeamount of heat is necessary due to the large water content. Also,ferricyanide ions damage the combustion furnace due to their strongoxidative power and further if the temperature in the combustion furnaceis lowered, undecomposed cyanide is discharged in the combustionproducts. Moreover, since the waste reducer solution contains athiosulfate, sulfur dioxide gas is generated on combustion, which causesair pollution.

The pyrolysis process is a process wherein a strong alkali is added tothe solution containing the ferricyanide ions and/or ferrocyanide ionsto adjust the pH of the solution over 12 and after heating the solutionto temperatures over 50C at normal pressure, a hypochlorite is addedthereto to decompose by oxidation the ferricyanide ions and/or theferrocyanide ions contained in the solution (Japanese Pat. applicationNo. 50,932/1971).

In this process the ferricyanide ions and/or ferrocyanide ions aredecomposed into iron oxide, carbon dioxide, carbonate, nitrogen andammonia. The advantage of this process is that, in contrast to theprocess of pre cipitating or concentrating ferricyanide ions and/orferrocyanide ions, such as the process of precipitating utilizing thereaction with an iron salt, a reverse osmosis process, and anelectrodialysis process, the ferricyanide ions and/or ferrocyanide ionsare completely decomposed into innocuous components and hence thisprocess is a complete final treatment eliminating the necessity offurther treatment.

However, since the waste reducer solution contains a large amount ofwater, the process requires also a large amount' of heat and large scaleequipment as in the case of the combustion process. Furthermore, sincethe waste reducer solution contains a thiosulfate, the hypochloriteadded to decompose by oxidation the ferricyanide ions and/orferrocyanide ions is readily reduced by the thiosulfate thereby losingits oxidative power.

Therefore, the treatment of ferricyanide ions and/or ferrocyanide ionsin a waste solution containing these ions in low concentration by theaforesaid pyrolysis process is a quite expensive.

As an economical process of treating waste water containing ferricyanideions and/or ferrocyanide ions in low concentration, a process oftreating the waste solution using a weakly-basic anion-exchange resin(see, Japanese Pat. Publication Nos. 92,1 15/1971, 22,907/1972, and52,267/1972, and US. Pat. application, Ser. No. 307,265, filed Nov. 16,1972) has been proposed. This process is quite profitable as compared toother processes as indicated above in the case of recoveringferricyanide ions and/or ferrocyanide ions as a concentrate from a largevolume of waste water containing these ions in low concentration.

However, the ferricyanide ions and/or ferrocyanide ions treated by thision-exchange process are still in the form of ferricyanide and/orferrocyanide ions and thus the problem of pollution occurs indischarging such residues. Namely, the ionexchange process has thedisadvantage that it is not a complete final treatment for the wastesolution.

SUMMARY OF THE INVENTION An object of this invention is, therefore, toprovide an economical and complete treatment process for removingefficiently ferricyanide ions and/or ferrocyanide ions from waste wateror a solution containing the ferricyanide ions and/or ferrocyanide ionstogether with thiosulfate ions in an innocuous dischargeable form.

This invention provides a process of treating waste water containingferricyanide ions and/or ferrocyanide ions which comprises bringing thewaste water containing these ions in contact with a weakly-basicanionexchange resin, removing the weakly-basic anionexchange resinhaving adsorbed thereon the ions from the waste water, immersing theweakly-basic anionexchange resin having the ions adsorbed thereon in analkaline solution to provide an alkaline concentrated solution of theions, adding to the concentrated solution a strong alkali, ahypochlorite, and bromide ions to adjust the pH of the solution to above12, and heating the mixture to temperatures above C at normal pressure,whereby the ferricyanide ions and/or the ferrocyanide ions aredecomposed.

According to another embodiment of this invention there is furtherprovided a process of treating waste water containing ferricyanide ionsand/or ferrocyanide ions which comprise bringing the waste water containing the ions in contact with a weakly basic anionexchange resin in thepresence of at least one of borate ions, a weak acid, and a weak acidsalt, removing the weakly-basic anion-exchange resin having adsorbedthereon the ions from the waste water, immersing the weakly-basicanion-exchange resin having the ions adsorbed thereon in an alkalinesolution to provide an alkaline concentrated solution of the ions,adding to this solution a strong alkali, a hypochlorite, and bromideions to adjust the pH of the solution to above 12, and heating themixture to temperatures above 50C, whereby the ferricyanide ions and/orthe ferrocyanide ions are decomposed.

DETAILED DESCRIPTION OF THE INVENTION It has already been discoveredthat when waste water containing ferricyanide ions and/orferrocyanideions together with thiosulfate ions is treated with a weaklybasicanion-exchange resin, the thiosulfate ions are not adsorbed but theferricyanide ions and/or ferrocyanide ions only are selectively adsorbedby the resin with good efficiency as described in the specification ofJapanese Pat. application No. 92,115/1971.

The inventors have further investigated the pyrolysis of ferricyanideions and/or the ferrocyanide ions and have discovered that the presenceof bromide ions is necessary for completely decomposing the ferricyanideions and/or ferrocyanide ions into innocuous materials. Namely, theinventors have conducted the pyrolysis of a solution containingferricyanide ions and/or ferrocyanide ions for investigating thepyrolysis of waste reducer solution and have confirmed that l to 10% byweight of the ferricyanide ions and/or ferrocyanide ions always remainin the treated solution, in other words, the decomposition reaction inthe pyrolysis is not complete. Thus, the inventors have alsoinvestigated the influence of various materials on the pyrolysis whenthey are present in the pyrolysis system and as the results thereof,have discovered that ferricyanide ions and/or ferrocyanide ions arecompletely decomposed by the pyrolysis only when bromide ions are prsentin the pyrolysis system,

Based on the above discovery that the presence of bromide ions isessential in the pyrolysis of ferricyanide ions and/or ferrocyanideions, the inventors have developed a complete decomposition treatment offerricyanide ions and/or ferrocyanide ions as an economical and finaltreatment for waste water containing ferricyanide ions and/orferrocyanide ions together with thiosulfate ions, by combining thetreatment of the waste water with a weakly-basic anion-exchange resinand the pyrolysis of a concentrated solution of ferricyanide ions and/orferrocyanide ions in the presence of bromide ions. The process of thisinvention is an excellent complete treatment for such'waste water.

That is to say, when a waste solution containing ferricyanide and/orferrocyanide ions and thiosulfate ions is contacted with a weakly-basicanion-exchange resin, the thiosulfate ions are not adsorbed by theionexchange resin and only ferricyanide ions and/or the ferrocyanideions are adsorbed on the ion-exchange resin. Therefore, the eluateobtained on regenerating the anion-exchange resin containing theadsorbed ions contains the ferricyanide and/or ferrocyanide ions onlyand does not contain any thiosulfate ions. Consequently, the eluate canbepy'rolyzed without.and reductive action of the thiosulfate on thehypochlorite, etc., and hence with the addition of a small amount ofions can be decomposed effectively and economically.

However, even when the eluate containing ferricyanide ions and/orferrocyanide ions without thiosulfate ions is subjected to a pyrolysistreatment, 1 to 10% by weight of the ferricyanide and/or ferrocyanideions still remain undecomposed. In other words, the completedecomposition of the ferricyanide ions and/or ferrocyanide ions requiresthe present of bromide ions as described above. By conducting thepyrolysis in the presence of bromide ions in accordance with thisinvention, the ferricyanide ions and/or the ferrocyanide ionscan becompletely decomposed. In the process of treating a waste solutioncontaining ferricyanide and/or ferrocyanide ions and thiosulfate ions bythe combination of the treatment with a weakly-basic anion-exchangeresin and a pyrolysis treatment, the complete decomposition of theferricyanide and/or ferrocyanide ions becomes possible only byconducting the pyrolysis in the presence of bromide ions in accordancewith this invention. The abovedescribed excellent effects are notobtained by the simple combination of the treatment with a weakly-basicanion-exchange resin and the pyrolysis treatment.

Also, since the eluate from the anion-exchange treatment is obtained asa solution concentrated about 100 to 500 times, the amount of wastewater to be subjected to the pyrolysis is H100 to 1/500 of the volume ofthe original waste solution or water before the anionexchange resintreatment. Thus, the equipment for the pyrolysis may be small and theamount of heat required for the pyrolysis may be small, which results inreducing greatly the cost of the treatment.

In the case of treating ferricyanide ions and/or ferrocyanide ions bypyrolysis, the efficiency of the pyrolysis reaction increases withincreasing concentrations of the ferricyanide ions and/or ferrocyanideions.

That is to say, the higher the concentration of the ferricyanide ionsand/or the ferrocyanide ions, the less is the amount of a chlorinecompound such as a hypochlorite which may be required, which iseconomical. Ordinarily, the concentration of ferricyanide ions and- /orferrocyanide ions most suitable for the pyrolysis treatment isl0,00020,000 p.p.m. as free cyanide ions and the concentration offerricyanide ions and/or ferrocyanide ions in the eluate recovered fromthe anionexchange resin treatment is in the aforesaid most suitablerange for the pyrolysis.

Also, the regeneration of the weakly-basic anionexchange resin isconducted usually with an alkaline solution, the eluate from theanion-exchange resin treatment has a high pH, and hence it isunnecessary to add additional alkali, if the alkalinity issufficientlyhigh, in the case of conducting the pyrolysis, which is also anadvantage of this invention.

Thus, according to the process of this invention, ferricyanide ionsand/or ferrocyanide ions present together with thiosulfate ions in wastewater from photographic processings or other industrial processings areadsorbed on a weakly-basic anion-exchange resin and then the eluate fromthe regeneration treatment of the anion-exchange resin is subjected tothe pyrolysis treatment in the presence of bromide ions to decomposecompletely the ferricyanide ions and/or the ferrocyanide ions in it.

On the other hand, Japanese Pat. application No. 22,907/1972 discloses aprocess of treating waste water containing ferricyanide ions and/orferrocyanide ions with a weakly-basic anion-exchange resin in thepresence of borate ions and further Japanese Pat. application No.52,267/1972 discloses a similar process in which a weak acid and/or aweak acid salt is used in place of the borate ions.

With those processes it has been confirmed that the exchange facility ofa weakly-basic anion-exchange resin to ferricyanide ions and/orferrocyanide ions .is increased and also the reduction in facility ofthe anionexchange resin after regeneration is greatly reduced by thepresence of the above-described material or materials.

As the result of further investigating the aforesaid prior inventions,the inventors have also discovered that ferricyanide ions and/orferrocyanide ions in a waste solution containing these ions togetherwith thiosulfate ions can be completely decomposed by combining theabove-described principal process of this invention and the aforesaidprocess of the prior invention. Namely, when waste water containingferricyanide and/or ferrocyanide ions and thiosulfate ions is treatedwith a weakly-basic anion-exchange resin after adding thereto at leastone of borate ions, a weak acid, and a weak acid salt and then theeluate recovered from the regeneration treatment of the anion-exchangeresin is subjected to a pyrolysis after adding bromide ions to theeluate, the ferricyanide ions and/or the ferrocyanide ions can becompletely decomposed as in the case of the principal process of thisinvention in which no additives such as the borate ions, the weak acid,and the weak acid salt are added. Furthermore, in this case ferricyanideions and ferrocyanide ions are selectively adsorbed by the weakly-basicanion-exchange resin, the thiosulfate ions are not adsorbed by theanionexchange resin, and hence no difficulties based on the reductiveaction of the thiosulfate in the pyrolysis are encountered. In otherwords, in the process of this invention at least one of borate ions, aweak acid, and a weak acid salt can be added to the waste watercontaining the aforesaid ions for further improving the ionexchangecapacity of the weakly-basic anion-exchange resin and preventing thereduction in the ion-exchange capacity of the anion-exchange resinwithout obstructing the effects and the features of this invention. Inthe second embodiment of the process of this invention, the capacity orfacility of the weakly-basic anionexchange resin can be increasedwithout obstructing the complete decomposition of the ferricyanide ionsand/or the ferrocyanide ions in the waste water.

Thus, according to the second embodiment of the process of thisinvention, at least one of borate ions, a weak acid, and a weak acidsalt is added to waste water containing ferricyanide and/or ferrocyanideions and thiosulfate ions, the waste water is treated with aweakly-basic anion-exchange resin, and the eluate obtained in theregeneration of the anion-exchange resin is subjected to a pyrolysistreatment in the presence of bromide ions.

The weakly-basic anion-exchange resins which can be used in the processof this invention are those composed of matrices such assytrene-divinylbenzene copolymer, a methacrylatedivinylbenzenecopolymer, a phenol-formaldehyde copolymer, etc., having at least one ofprimary amines, secondary amines, and tertiary amines as theion-exchange group. That is to say, if the weakly-basic anion-exchangeresin has at least one of a primary amine, a secondary amine, and atertiary amine, the matrix of the anion-exchange resin can be of anykind of resin, can be prepared in any manner, can have anypolymerization degree and any fine structure such as, e.g., a gelstructure, a porous structure, etc., and can be processed in any manner.

Typical commercially available weakly-basic anionexchange resins arethose sold under the trade names of Diaion WA-lO, Diaion WA-l I, DiaionWA-20, Diaion WA-ZI, and Diaion WA-3O (made by Mitsubishi ChemicalIndustries Co., Ltd.), Amberlite IRA-45, Amberlite IRA-93, AmberliteIR-4B, and Amberlite IRP-58 (made by JAPAN Organo Co., Ltd), andDower-44 (made by Dow Chemical Co.). The weakly-basic anion-exchangeresins used in this invention are, however, not limited to thesematerials as illustrated above. The structures of a few anion-exchangeresins of the abovedescribed commercially available materials are shownbelow:

Diaion WA-lO:

Diaion WA:

Diaion WA-301 wherein m and n are an integers.

The particularly regenerable weakly-basic anionexchange resins of thosewhich can be used in the process of this invention are those havingtertiary amine as the ion-exchange functional group and of them a particularly excellent weakly-basic anion-exchange resin is Diaion WA-lO.When a weak acid and/or a weak acid salt is present, those weakly-basicanion-exchange resins have the highest ion-exchange facility toferricyanide ions and/or ferrocyanide ions per volume of the resin andcan be most easily regenerated.

As the weakly-basic anion exchangc resin, there are a free-base type anda salt type but the commercially available ones are generally free basetype resins. Both the free base type resin and the salt type resin canbe used in this invention but the free base type resin is generally usedfrom the standpoint of availability.

The Weakly-basic anion-exchange resin ionexchanged by ferricyanide ionsand/or ferrocyanide ions is generally regenerated using an alkainesolution. As the alkaline solution, there are illustrated an aqueoussolution of an alkali metal hydroxide such as sodium hydroxide, andpotassium hydroxide, an aqueous solution of an alkali metal carbonatesuch as sodium carbonate and potassium carbonate, and an aqueoussolution of ammonia. In the case of using the salt-type weak-basicanionexchange resin, the resin is regenerted with an aqueoushydrochloric acid solution or an aqueous sodium chloride solution. Theconcentration of the regeneration agent or eluent is about 1 to 20% byweight, in particular 2 to 10% by weight.

Examples of compounds containing borate ion which can be used in thisinvention are boric acid, metaboric acid, and water-soluble borates suchas sodium borate, potassium borate, ammonium borate, and sodiummetaborate. Boric acid and/or the borates as illustrated above can beadded to the waste water containing ferricyanide ions and/orferrocyanide ions from photographic processings or other industrialprocessings and in particular, in the case of photographic processings,boric acid and/or the borate can be added to a photographic processingsolution such as a bleach solution, a blix solution, and a reducer. Theamount of boric acid and/or the borate used in this invention is usuallyin the range of 1/10 to 10 times the total of the moles of theferricyanide ions and the ferrocyanide ions in the waste water fromphotographic processings or in a photographic processing solution suchas a bleach solution, a blix solution, and a reducer. In particular, itis preferred that an amount ranging from 1/5 to 10 times the total ofthe moles of the ferricyanide ions and/or the ferrocyanide ions be used.

Examples of compounds including the weak acid and/or the weak acid saltwhich can be used in this invention are organic acids such as aceticacid, citric acid, maleic acid, fumaric acid, oxalic acid, tartaricacid, formic acid, malonic acid, phthalic acid, succinic acid, and thelike; the alkali metal salts of theseorganic acids; the ammonium saltsof these organic acids; inorganic weak acids such :as phosphoric acid,boric acid, sulfurous acid, and the like; the alkali metal salts ofthese inorganic acids, and the ammonium saltsof these inorganic acids.The weak acid and/or the weak acid salt as'illustrated above can beadded "to the waste watercontaining ferricyanide ions and/orferrocyanide ions and also in theease of photographic'processings,

it can be added to the processing solution suchas a reducer. Forexample, when theammonium salt is used for the treatment of the wastewater .Farmersreducer, thesame effect is obtained by using ammoniumthiosulfate as the thiosulfate. The. amount of the weakacid and/or theweak acid salt is in the range of 1/10 to.10

times the total numberof-molesof the ferricyanide ionsand/or theferrocyanide ions in the waste water..ln particular, it is preferredthat an amount ranging from 1/5 to times the total number of moles ofthe ferricyanide ions and/or ferrocyanide ions be-used.

According to the process of this invention waste water containingferricyanide ions and/or ferrocyanide ions'in any concentration can betreated but the process of this invention can be particularlyadvantageously applied to waste water containingferricyanide ions and/orferrocyanide ions in aconcentration lower than 3,000 p.p.m., inparticular to waste waterhaving aconcentration lower-then 1,000 ppm.

The processof this inventionis also applicable to waste water containingthiosulfateions in an amount of lower than about 150 times the totalnumberof moles.

of the ferricyanide ions and ferrocyanide ions contained in the wastewater. The process is preferably applied to waste water containingthiosulfate ions in an amount of. lower than 100 times the total numberof moles of the ferricyanide ions and/or. the ferrocyanide ions thereinand in particular the I process is applied more particularly to wastewater containing thiosulfate ions in an amount of lower than 50 timesthe total number of moles of the ferricyanide ions and/or theferrocyanide ions. o

The contact between the waste water containing ferricyanide and/orferrocyanide ions and thiosulfate ions.

and the weakly-basic anion-exchange resin can be practiced by anymethod.

In general, the contacting iswith the weakly-basic an-. ion-exchangeresin filled in a cylindrical vesselor a column to provide a layer orzone of the ion-exchange resin and then the wastewater is passed throughtheion-exchange resin layer or zone from the top to the bottom but asthe case may be, the waste water may be passed from the bottom tothetop. According to a manner such as is mentioned abov.e, ferricyanideions and- /or ferrocyanide ions" can be continuously. removed from thewaste water. As the case may be, however, the ion-exchange. treatmentcan be conducted by adding the weakly-basic anion-exchange resin tothewaste water stored-followed by stirring, allowing "the :ion exchangeresin to settle, and recovering the resin by filtration. *However, anadvantage in using .the ion-. exchange resin is that the treatment canbe continuously conducted and hence passing the waste water continuouslythrougha weakly-basic anionexchange resin column is preferred tothe-above described batch method. I

The regeneration of the weakly-basic anionexchange resin thusion-exchanged with the ferricyanide ionsand/or the ferrocyanide ions isconducted using. analkaline aqueous .solution, As the alkaline aqueoussolution, there are illustrated aqueous solutions of art-alkali metalhydroxide such as sodium hydroxide and potassium hydroxide-,an aqueoussolution of an alkali metal carbonate such, as sodium carbonate andpotassium carbonate, and an aqueous solution of ammonia. Theconcentration of the solution used for the regeneration is about 1to-20% by weight, preferably 2 to 10% by weight.

The contact between the alkaline aqueous solution and the weakly-basicanion-exchange resin having ions absorbed thereon can be conducted byany manner. For example, the technique described above in the contactbetween the waste water and the anionexchange resin can be utilized inthe regeneration method also.

By conducting the regeneration of theweakly-basic anion-exchange resin,the ferricyanide ions and/or the ferrocyanide ionsare removed fromtheweakly-basic. anion-exchange resin, that is to say, the solution or theeluate containing the ferricyanide ions and/or the ferrocyanide ions isremoved or recovered from the ionexchange system. The eluate containsusually the ferri-' cyanide ions and/or ferrocyanide ions in a highconcentration of ordinarily 10,000 to 100,000 ppm. The eluate can bequite conveniently subjected to pyrolysis since it has a high alkalinityand further it contains no salts such as a thiosulfate.

Examples of compounds. containing. bromide ions which can be used thepyrolysis in thepresent invention are alkali metal bromides such aspotassium bromide and sodium bromide; alkaline earth metal bromidessuch-as calcium bromide, barium bromide, and magnesium bromide; andmeta] bromides such as aluminum bromide and iron bromide. Ammoniumbromide can be also used in this invention for the same purpose.Basicallyflthe water-soluble bromies other than those heavy metalbromides catalytically promoting the decomposition of the hypochlorite,suchas copper bromide and nickel bromide, can be used in this invention.The concentration of the bromide-ions depends-upon the concentration ofthe ferricyanide ions and/or the ferrocyanide ions but his better to usean aqueous solution of thebromide having a content of higher than 0.1glliter as'bromide ions. A particularly preferred content of thebromideions is over 0.5 g/liter.

Since the alkali metal bromides and ammonium bromide are readilyavailable, usually they are used for the pyrolysis treatment.

Examples of the alkali which can be used in the pyrolysis of thisinvention are alkali metal hydroxides such as'sodium hydroxide andpotassium hydroxide and alkali metal carbonates such as sodium carbonateand potassium carbonate. That is to say, the alkali used for theregeneration of the weakly-basic anion-exchange resin having thereon theferricyanide ions and/or ferrocyanide ions can be used for the pyrolysisin situ.

Examples of suitable hypochlorites .which can be used in the pyrolysisare sodium hypochlorite, potassium hypochlorite, andcalcium'hypochlorite. Furthermore, chlorine can alsobe usedfor thepurpose. The addition of the alkali is conducted so that the pH of thesystem is above 12 and in particular better results are obtained thecloser the pH is to 'a-pl-l of-'l4. The eluate used for the regenerationof the weakly-basic anionexchange resin inthis invention usually has apH higher than 12 and in such a case it is unnecessary to add an alkalito the pyrolysis system, which is quite convenient.

The process of this invention can be applied to any waste solutionscontaining ferricyanide and/or ferrocyanide ions and thiosulfate ionsand in particular is suitable for the treatment of waste water fromphotographic processings.

In the steps of processing silver halide color photographic materials, asolution containing a ferricyanide is used as a bleach solution and asolution containing a thiosulfate is used as fix solution. Therefore, bydeveloping silver halide color photographic materials, waste watercontaining ferricyanide and/r ferrocyanide ions and thiosulfate ions isformed or discharged. Such waste water can contain acid sodiumphosphate, potassium alum, and a pH adjusting agent such as sodiumhydroxide, glacial acetic acid, sodium acetate, sodium phosphate, etc.Also, in the processing of reversal silver halide color photographicmaterials, a bleach solution containing a ferricyanide is used incombination with a fix solution containing a thiosulfate, which resultsin forming waste water containing ferricyanide and/or fer rocyanide ionsand thiosulfate ions. Furthermore, it sometimes happens that theferricyanide and/or ferrocyanide ions and thiosulfate ions are carriedover in the washing water from the fix solution in which theferricyanide and/or ferrocyanide ions have been carried over.

The waste water containing such ferricyanide and/or ferrocyanide ionsand thiosulfate ions is passed through a weakly-basic anion-exchangeresin, the ferricyanide ions and/or the ferrocyanide ions are recoveredby regenerating the anion-exchange resin as a concentrated solution ofthese ions without the thiosulfate ions, and then the ferricyanide ionsand the ferrocyanide ions contained in the concentrated solution can becompletely decomposed into innocuous materials by subjecting thesolution to pyrolysis in the presence of the bromide ions. That is tosay, in the pyrolysis of this invention, the ferricyanide ions and/orthe ferrocyanide ions are decomposed into ferric hydroxide, ferric oxide, nitrogen, carbon dioxide, and alkali metal carbonates. The ferrichydroxide and ferric oxide thus formed can be easily removed from thesolution using known techniques and the amount thereof is generallyquite small. Namely, according to the process of this invention, asolution containing ferricyanide ions and/or ferrocyanide ions and notcontaining any thiosulfate ions can be obtained from waste watercontaining ferricyanide and/or ferrocyanide ions and thiosulfate ions asthe concentrated solution thereof, which is quite convenient for thesubsequent pyrolysis treatment. As described above, with the removal ofthiosulfate, the loss of the oxidizing agent such as a hypochlorite canbe prevented and further since the solution containing the ferricyanideions and/or the ferrocyanide ions is obtained as a concentratedsolution, the efficiency of the pyrolysis is increased and the volume ofthe solution to be treated in the pyrolysis is small. Therefore, theprocess of this invention provides quite excellent economical advantagessuch various aspects as chemicals, equipment, and energy which are used.

Also, since according to the process of this invention the pyrolysis is100 percent efficient due to the presence of the bromide ions, theferricyanide ions and/or the ferrocyanide ions can be completelyconverted into innoculous materials and thus the problem of dischargingprecipitates containing these noxious materials encountered in the caseof employing various aggregation and precipitation processes can becompletely eliminated. Thus, the waste water containing ferricyanideions and ferrocyanide ions can be completely treated in an economicalmanner by the process of this invention. As described above, a quitelarge advantage can be obtained by combining the process of using theweaklybasic anion-exchange resin for the treatment of waste watercontaining ferricyanide and/or ferrocyanide ions and thiosulfate ionsand the process of pyrolyzing the eluate containing the ferricyanideions and ferrocyanide ions only recovered from the regenerationtreatment for the anion-exchange resin in the presence of bromide ionsaccording to the process of this invention.

The process of this invention has the following excellentcharacteristics:

I. Since large and expensive equipment as in the case of employing anelectrodialysis, a reverse osmosis, and an aggregation and precipitationprocess is not required, the space requirements can be small and theequipment cost is low in the process of this invention.

2. Since precipitates containing ferricyanide ions and/or ferrocyanideions as encountered in the case of employing various aggregation andprecipitation processes are not formed in the process of this invention,pollution problems by discharging the waste treated in the process ofthis invention does not result.

3. There are no problems of causing pollution with undecomposed cyanidegas, sulfur dioxide gas, and smoke as in the case in employing acombustion pro cess and furthermore a large amount of fuel is notrequired.

4. Since the anion-exchange resin can be used repeatedly afterregeneration, which is also a step of the process of this invention, theprocess is quite economical.

5. The process of this invention is excellent in comparison with theconventional simple pyrolysis from the standpoint that the ferricyanideions and/or the ferrocyanide ions can be completely decomposed and alsothe chemicals, energy, and equipment necessary for the process of thisinvention can be less, which makes this process quite economical.

Now, the invention will be explained further in greater detail byreference to the following examples but the invention is not to beinterpreted as being limited to the examples only. Unless otherwiseindicated, all percents and parts are by weight.

EXAMPLE 1 In a plastic column having an inside diameter of 4 cm wasfilled 500 ml of a weakly-basic anion-exchange resin, Diaion WA-lO(trade name, made by Mitsubishi Chemical Industries Co., Ltd.), asolution prepared by diluting Farmers reducer having the compositionshown below by about times with water and adding 0.3 g/liter of boricacid was passed through the ionexchange resin as an example of wastewater, and then the composition of the water passed through theionexchange resin column was analyzed.

Composition of Farmers Reducer: Solution A: 37.5 g of ferricyanide wasdissolved in water to make a solution of 500 ml.

Solution B: 480 g of anhydrous sodium thiosulfate was dissolved in waterto make a solution of 2 liters.

Immediately before use, Solution A was mixed with I Solution B in avolume ratio of l 4.

The sample waste water thus prepared had the following compositionfFerricyanide ions and ferrocyanide ions:

[Fe(CN) and Fe(CN) 100 p.p.m. as CN- Anhydrous Sodium Thiosulfate (Na SO 2.7

g/liter Boric Acid (H BO 0.3 g/liter The sample waste water preparedabove was passed through the ion-exchange resin column and the waterprocessed by the ion-exchange resin was analyzed after processing 1liter and then 100 liters of the waste water. The results obtained areshown in the following table.

Table 1 Material Present After Treating After Treating 1 Liter I LitersFerricyanide ions less than 0.5 less than 0.5 and ferrocyanide ionsp.p.m. as CN" p.p.m. as CN Anhydrous sodium 26 g/liter 2.7 g/literthiosulfate The analysis of the ferricyanide ions and ferrocyanide ionswas conducted by measuring the spectral absorption of the visibleportion of the blue color formed by adding a diluted sulfuric acidsolution of 5% ferrous sulfate. The analysis of sodium thiosulfate wasconducted by iodometry.

From the above results it was confirmed that the thiosulfate wasadsorbed by the weakly-basic anionexchange resin to a lesser degreewhile the ferricyanide ions and the ferrocyanide ions were selectivelyadsorbed.

Furthermore, when the sample waste water was treated with theion-exchange resin, 220 liters of the sample water could be treated inone run until the content of the ferricyanide ions and ferrocyanide ionsin the treated water was higher than I p.p.m. as CN'.

After treating 220 liters of the waste water, the ionexchange resin wasregenerated using 1 liter ofa 4% by weight aqueous solution of sodiumhydroxide and the eluate recovered in the regeneration was subjected toa pyrolysis treatment. The eluate had the following composition: pH:13.9.

Ferricyanide ions and ferrocyanide ions: p.p.m. as CN- The eluate havingthe above composition was placed in five beakers in an amount of 200 mleach and after adding thereto aqueous sodium hypochlorite solution(containing 123.0 g/liter of NaOCl) in the amount as shown in Table 2,the mixture was maintained at 85C to conduct the reaction for 2 hours.Furthermore, 8- g of sodium hydroxide was added to the mixture in thebeakers ofTest No. 2 and Test No. 4 and 0.4 g of potassium bromide .wasadded in the beaker of Test Number After 2 hour's the reaction was over,water was added to the mixture to make the total volume 200 ml tocompensate for the evaporated water and then the content of theferricyanide and the ferrocyanide remaining in the solution wasmeasured.

The measurementof 'the total cyanide content was conducted according tothe methods of HS-K0102- 29.1.2 and .IISKO102-29.2. I

Theresults obtained are shown in the following table.

Table 2 Test No. NaOCl NaOI-l KBr Total Cyanide Content Remaining (p 1 Ig None None 520 2 I85 g 8 g None 2,120 3 27.8 g None None 410 4 27.8 g 8g None 880 5 18.5 g None 0.4 g Undetected From the above results, it wasconfirmed that the ferricyanide ions and the ferrocyanide ions presentin the eluate recovered from the ion-exchange resin regeneration percentwere decomposed when the bromide ions were present.

EXAMPLE 2 An aqueous solution containing 10.6 g/liter of potassiumferricyanide (K [Fe(CN) and 13.5 g/liter of potassium ferrocyanide (K[Fe(CN) 3H O) was prepared and it was experimentally confirmed usingthis aqueous solution that the presence of the bromide ions wasessential for completely decomposing the ferricyanide ions and theferrocyanide ions in the pyrolysis treatment.

That is to say, 25 g of sodium hydroxide and 25 g of sodium hypochlorite(an aqueous solution of 103 g/liter of sodium hypochlorite was used)were added to 500 ml of the aqueous solution prepared above and theresultant solution was maintained at 85C with the reaction beingconducted for 6 hours. In the cases of test numbers 7-10, the bromide asshown in Table 3 was added to the solution before heating in an amountof 0.5 g as bromide ions,

After reacting for 3 hours or 6 hours, the total cyanide contentremaining was measured in each case. The analysis of the total cyanidecontent was made according to the methods of JIS-K0lO2-29.1.2 and HS-K0l02-29.2.

Table 3 Test No. Bromide After Reacting After Reacting for 3 Hours for 6Hours 6 None 2,450 ppm 2,200 ppm 7 KBr Undetected Undetected 8 Nl-l BrUndetected Undetected 9 CaBr Undetected Undetected l0 AlBn UndetectedUndetected From the above results it was confirmed that only when thebromide ions were present did the pyrolysis reaction of the ferricyanideions and the ferrocyanide ions proceed to the extent of 100 percent.

EXAMPLE 3 plate while washing the surface with water continuously toconduct the reduction and collecting the washing water containing theFarmers reducer.

Composition of Farmers Reducer:

Solution A: 37.5 g of potassium ferricyanide was dissolved in water tomake 500 ml of total volume.

Solution B: 650 ml of ammonium thiosulfate (70% solution) was dissolvedin water to make 2 liters of total volume.

Immediately before use, Solution A was mixed with Solution B in a volumeratio of l 4.

The concentration of the ferricyanide ions and/or the ferrocyanide ionsin the Farmers reducer waste water varied over the range of to about 200p.p.m. as total cyanide but the mean concentration of these solutionswas about 100 p.p.m. as total cyanide. The waste water was passedthrough the above-described ion-exchange resin column until theconcentration of the ferricyanide ions and the ferrocyanide ions in thetreated water became greater than 1 p.p.m. as total cyanide content.

Then, after washing the anion-exchange resin with water, theanion-exchange resin was regenerated by passing through theanion-exchange resin liters of an aqueous 6% potassium hydroxidesolution at a rate of 500 ml/min. Then, after washing the anionexchangeresin sufficiently with water, the above-described waste water waspassed through the anion-exchange resin col umn and then theanion-exchange resin was regenerated again. This ion-exchange andregeneration cycle was repeated a total of four times. The amount of thewaste water passed through the ion-exchange resin column until thecontent of the ferricyanide ions and ferrocyanide ions in the treatedwaste water became greater than 1 p.p.m. as total cyanide content was 4tons on the average in each case. The amount, the pH, and the totalcyanide content in the eluate recovered in the fourth regenerationtreatment were as follows.

Amount of the eluate: 14 liters pH: 13.7 Total cyanide content: l7,l00p.p.m.

Then, an aqueous solution of sodium hypochlorite (containing 123 g/literof NaOCl) was added to 500 ml of the eluate having the above compositionso that the content of the sodium hypochlorite became 0.5 g and afterfurther adding to the solution ammonium bromide at a level of 0.5 g asbromide ions, the mixture was heated to 8085C for 2 hours to conduct thereaction. Thereafter, water was added to the mixture to make 500 ml intotal volume to compensate for the evaporated water and the analysis ofthe total cyanide content was conducted. The analysis in each case wasconducted according to the method of JIS K0l02-29.l.2 and .115K0l02-29.2. The total cyanide content was 0.03 p.p.m.

EXAMPLE 4 In each of the two cylinders having an inside diameter of 4.5cm was filled 30 ml of a weakly-basic anionexchange resin, Diaion WA-ll(trade name, made by Mitsubishi Chemical Industries Co., Ltd.). Then, asolution prepared by diluting by 100 times a bleach solution having thefollowing composition with water was passed through one of theion-exchange resin columns at a rate of 300 ml/min.

Composition of the Bleach Solution:

Ferricyanide: lOO g Potassium bromide 30 g Water to make 1 liter Asolution prepared by diluting by times a bleach solution having theabove composition with water and further adding thereto 1.0 g/liter ofboric acid was passed through another ion-exchange resin column at arate of 300 ml/min.

The amount of the treated solution until the ferricyanide ions weredetected (treatment facility) was measured for each ion-exchange resincolumn. Then, the ion-exchange resin column in which the ferricyanideions were detected in the treated solution was regenerated in the sameway as described in Example 1 and then a solution prepared by dilutingby 100 times the bleach solution with water or a solution prepared bydiluting by 100 times the bleach solution with water and adding thereto1.0 g/liter of boric acid was passed through the regeneratedion-exchange resin column. The results obtained are shown in thefollowing table.

Test Additive to Diluted Treatment Facility liter As shown in the abovetable, where no boric acid was added to the diluted bleach solution, theweakly-basic anion-exchange resin showed no ionexchange capacity for theferricyanide ions but where boric acid was added to the diluted bleachsolution, the anionexchange resin showed a good ion-exchange facility tothe ferricyanide ions. Also, the treatment facility of the weakly-basicanion-exchange resin was quite high in the case of adding boric acid andfurther, the reduction in treatment facility of the anion-exchange resinafter regeneration was quite low in the case of adding boric acid.

Then, when the ferricyanide ions and ferrocyanide ions present in theeluate recovered from the regeneration step of the anion-exchange resinwere decomposed in the same way as described in Example 1, they werecompletely decomposed.

EXAMPLE 5 In each of two cylindrical columns having an inside diameterof 4.5 cm was filled 300 ml of a weakly-basic anion-exchange resin,Diaion WA-l I (trade name, made by Mitsubishi Chemical Industries, Co.,Ltd.). A solution prepared by diluting by 100 times a bleach solutionhaving the following composition with water was passed through one ofthe ion-exchange resin columns at a rate of 300 ml/min.

Composition of Bleach Solution:

loo' I v l liter Ferricyanide: Potassium bromide: Water to make.

solution having the above composition with water and adding thereto 2.0g/liter of sodium dihydrogenphosphate was passed through anotherion-exchange resin column at a rate of 300 ml/min. Then, the amount ofthe solution passed through each ion-exhange resin column until theferricyanide ions were detected in the treated solution (treatmentfacility) was measured in each case.

Thereafter, the anion-exchange resin which showed the ferricyanide ionsin the treated solution was regenerated in the same way as described inExample 1 and then a solution prepared by diluting by 100 times thebleach solution of the solution prepared by diluting by 100 times thebleach solution and adding 2.0 g/liter of sodium dihydrogenphosphate waspassed through the regenerated ion-exchange resin column., The resultsobtained are shown in the following table.

Test Additive to Diluted Treatment Facility phosphate 2.0 g/ liter Asshown in the above table, where no sodium dihydrogenphosphate was addedto the diluted bleach solution, the weakly-basic anion-exchange resinshowed no ion-exchange facility for the ferricyanide ions, while in thecase of adding sodium dihydrogenphosphate, the anion-exchange resinshowed good ion-exchange facility for the ferricyanide ions.Furthermore, in the case of adding sodium dihydrogenphosphate, thetreatment facility of the anion-exchange resin was quite high andfurther the reduction in the treatment facility of the anion-exchangeresin after regeneration was quite low.

Then, when the ferricyanide ions and the ferrocyanide ions in the eluaterecovered from the regeneration treatment of the anion-exchange resinwere decomposed in the same way as describedin Example 1, they werecompletely decomposed.

While the invention has been described in detail and with reference tospecific embodiments thereof, it will be apparent to one skilled in theart that various changes and modifications can be made therein withoutdeparting-from the spirit and scope thereof.

What is claimed is: I

1. A process of treating waste water containing ferricyanide ions andferrocyanide ions which comprises bringing said waste water containingthese ions into contact with a weakly-basic anion-exchange resin foradsorption of ferricyanide and ferrocyanide ions on said resin, removingsaid weakly-basic anion-exchange resin having adsorbed thereonferricyanide and ferrocyanide ions from said waste water, immersing said.18 weaklwb asic, anion-exchange resin having said ferricyanide andferrocyanide,..ions adsorbed. thereoninto an alkaline solu tionitb'provide .an alkaline concentrated solution of ,said, ferricyanide. and.ferrocyanide ions, adding .to.is aid alkaline concentrate'd" solution astrong alkali, a hypochlorite,.andbromide ions, so that the pH ofsaidsolution is above 1 2, and heating said solution to temperatureswabout 509C .:at? normal. pressure,

whereby said ferricyanide and ferrocyanide ions are decomposed, whereinsaid bromide ions serve to accelerate the heat decomposition offerricyanide ions and ferrocyanide ions during said heating.

2. The process of claim 1, wherein said bringing of said waste waterinto contact with said weakly-basic anion-exchange resin is in thepresence of at least one group consisting of boric acid, metaboric acid,or

water-soluble borate salts.

6. The process of claim 5, wherein said borate ions are present in anamount of from US to 10" times the total of the moles of saidferricyanide ions and said ferrocyanide ions present.

7. The process of claim 2, wherein said weak acid is selected from thegroup consisting of an organic acid and an inorganic acid.

8. The process of claim 7, wherein said organic acid is selected fromthe group consisting of acetic acid, citric acid, maleic acid, fumaricacid, oxalic acid, tartaric acid, formic acid, malonic acid, phthalicacid, or succinic acid, and wherein said inorganic acid is selected fromthe group consisting of phosphoric acid, boric acid, or sulfurous acid.

9. The process of claim 2, wherein said weak acid salt is a memberselected from the group consisting of an alkali metal salt or anammonium salt of a member selected from the group consisting of a weakorganic acid and a weak inorganic acid.

10. The process of claim 9, wherein said weak acid salt is a memberselected from the group consisting of an alkali metal salt and anammonium salt of a member selected from the group consisting of aceticacid, citric acid, maleic acid, fumaric acid, oxalic acid, tartaricacid, formic acid, malonic acid, phthalic acid, succinic acid,phosphoric acid, boric acid, and sulfurous acid.

11. The process of claim 2, wherein said member selected from the groupconsisting of said weak acid and said weak acid salt is present at from1/10 to 10 times the total numer of moles of said ferricyanide ions andsaid ferrocyanide ions in said waste water.

12. The process of claim 1, wherein said waste water additionallycontains thiosulfate ions.

13. The process of claim 1, wherein said waste water is waste water fromphotographic processings.

14. The process of claim 1, wherein said ferricyanide ions and saidferrocyanide ions are present in said waste water at a concentrationlower than 3,000 ppm.

15. The process of claim 1, wherein said alkaline solution comprises asolution of a member selected from ions are from a compound containingbromide ions, said compound being a member selected from the groupconsisting of an alkali metal bromide, an alkaline earth metal bromide,a water soluble metal bromide, or

ammonium bromide.

19. The process of claim 18, wherein said bromide ions are present at aconcentration of higher than 0.1 g/liter.

1.A PROCESS FOR TREATING WASTE WATER CONTAINING FERRICYANIDE IONS ANDFERROCYANIDE IONS WHICH COMPRISES BRINGING SAID WASTE WATER CONTAININGTHESE IONS INTO CONTACT WITH A WEAKLYBASIC ANION-EXCHANGE RESIN FORADSORPTION OF FERRICYANIDE AND FERROCYANIDE IONS ON SAID RESIN, REMOVINGSAID WEAKLY-BASIC ANION-EXCHANGE RESIN HAVING ADSORBED THEREONFERRICYANIDE AND FERROCYANIDE IONS FROM SAID WASTE WATER, IMMERSING SAIDWEAKLY-BASIC ANION-EXCHANGING RESIN HAVING SAID FERRICYANIDE ANDFERROCYANIDE IONS ADSORBED THEREON INTO AN ALKALINE SOLUTION TO PROVIDEAN ALKALINE CONCENTRATED SOLUTION OF SAID FERRICYANIDE AND FERROCYANIDEIONS, ADDING TO SAID ALKALINE CONCENTRATED SOLUTION A STRONG ALKALI, AHYPOCHLORITE, AND BROMIDE IONS SO THAT THE PH OF SAID SOLUTION IS ABOVE12, AND HEATING SAID SOLUTION TO TEMPERATURES ABOUT 50*C AT NORMALPRESSURE, WHEREBY SAID FERRICYANIDE AND FERROCYANIDE IONS AREDECOMPOSED, WHEREIN SAID BROMIDE IONS SERVE TO ACCELERATE THE HEATDECOMPOSITION OF FERRICYANIDE IONS AND FERROCYANIDE IONS DURING SAIDHEAING.
 2. The process of claim 1, wherein said bringing of said wastewater into contact with said weakly-basic anion-exchange resin is in thepresence of at least one member selected from the group consisting ofborate ions, a weak acid and a weak acid salt.
 3. The process of claim2, wherein said waste water additionally contains thiosulfate ions. 4.The process of claim 3, wherein said waste water is waste water fromphotographic processings.
 5. The process of claim 2, wherein said borateions are from a compound containing borate ions, said compoundcontaining borate ions being selected from the group consisting of boricacid, metaboric acid, or water-soluble borate salts.
 6. The process ofclaim 5, wherein said borate ions are present in an amount of from 1/5to 104 times the total of the moles of said ferricyanide ions and saidferrocyanide ions present.
 7. The process of claim 2, wherein said weakacid is selected from the group consisting of an organic acid and aninorganic acid.
 8. The process of claim 7, wherein said organic acid isselected from the group consisting of acetic acid, citric acid, maleicacid, fumaric acid, oxalic acid, tartaric acid, formic acid, malonicacid, phthalic acid, or succinic acid, and wherein said inorganic acidis selected from the group consisting of phosphoric acid, boric acid, orsulfurous acid.
 9. The process of claim 2, wherein said weak acid saltis a member selected from the group consisting of an alkali metal saltor an ammonium salt of a member selected from the group consisting of aweak organic acid and a weak inorganic acid.
 10. The process of claim 9,wherein said weak acid salt is a member selected from the groupconsisting of an alkali metal salt and an ammonium salt of a memberselected from the group consisting of acetic acid, citric acid, maleicacid, fumaric acid, oxalic acid, tartaric acid, formic acid, malonicacid, phthalic acid, succinic acid, phosphoric acid, boric acid, andsulfurous acid.
 11. The process of claim 2, wherein said member selectedfrom the group consisting of said weak acid and said weak acid salt ispresent at from 1/10 to 105 times the total numer of moles of saidferricyanide ions and said ferrocyanide ions in said waste water. 12.The process of claim 1, wherein said waste water additionally containsthiosulfate ions.
 13. The process of claim 1, wherein said waste wateris waste water from photographic processings.
 14. The process of claim1, wherein said ferricyanide ions and said ferrocyanide ions are presentin said waste water at a concentration lower than 3,000 ppm.
 15. Theprocess of claim 1, wherein said alkaline solution comprises a solutionof a member selected from the group consisting of an alkali metalhydroxide, an alkali metal carbonate, or ammonia.
 16. The process ofclaim 15, wherein the concentration of said alkali solution is about 1to 20% by weight.
 17. The process of claim 1, wherein said hypochloriteis a member selected from the group consisting of sodium hypochlorite,potassium hypochlorite, calcium hypochlorite, or chlorine in an aqueousalkaline solution.
 18. The process of claim 1, wherein said bromide ionsare from a compound containing bromide ions, said compound being amember selected from the group consisting of an alkali metal bromide, analkaline earth metal bromide, a water soluble metal bromide, or ammoniumbromide.
 19. The process of claim 18, wherein said bromide ions arepresent at a concentration of higher than 0.1 g/liter.